[Sidefx-houdini-list] water droplets running off the side of a bottle

Olivier Jeannel facialdeluxe at gmail.com
Thu Jan 21 05:24:54 EST 2016


Cool !

On Thu, Jan 21, 2016 at 10:49 AM, Gerbrand Nel <g at cannonballbunny.com>
wrote:

> Thanks everyone!!!
> Thanks to you guys, my client is happy.
> I never got to the double cross product, the bottle is standing upright,
> so a simple "move to centre in x and z" force made the drops stick to the
> bottle just fine :)
>
> I started with the rain otl on orbolt, to get the trail spawning going.
> I also spawned another trail with a life of 100 to generate a wetmap.
> I used attribute transfer to extract the bottle geo around these
> particles, and used some noise displacements on these for the water trail.
> The same wetmap particles had a pscale of 0, so I used another attribute
> transfer with a small radius, on the other droplets on the bottle, to fake
> the absorption of droplets as the main drop travelled down the bottle.
>
> I didn't use the liquid surface sop, I couldn't figure out how to get it
> to look at pscale, so I used a copy sop with spheres, and a vdb from
> polygons to create the liquid surface.
>
> The scene is a mess, but I will gladly share it if anyone needs to do
> something like this.
> G
>
>
>
> On 20/01/2016 21:46, Personal wrote:
>
>> Great idea with cross product. Would never thought about that, I am so
>> crap in math. But it works nice.
>>
>>
>> --
>> Micic Srecko
>> -------------------
>> Mail:
>> srecko.micic at gmail.com
>> Skype:srecko.micic
>> -------------------
>> On 19/01/2016 21:39:07, Olivier Jeannel <facialdeluxe at gmail.com> wrote:
>> The double cross product can be copied from Softimage's "flow on surface".
>> The principe is the same.
>>
>> If you want to use the SDF,inside Popvop you'll gather the distance from
>> an SDF surface using a Volume_Sample (if the value is negative the
>> particle
>> is inside, if it is positive the particle is outside, and if it returns
>> zero you're on the surface)
>> You sample the direction (equivalent to the Normal but for an SDF) using a
>> Volume_Gradient.
>>
>> Just be focused, and respect the cross product order and normalize
>> everything.
>> You'll end up with a plate of spagehties, but it works.
>>
>> On Tue, Jan 19, 2016 at 7:16 PM, Gerbrand Nel wrote:
>>
>> Thanks everyone!!
>>> I shall try
>>> found this one too:
>>> https://vimeo.com/40954039
>>> Bit over the top for my 1 day budget, but there are some nice ideas in
>>> there.
>>> G
>>>
>>> On 19/01/2016 19:49, Javier Meroño wrote:
>>>
>>> if you want a reusable tool for dripping droplets like this one
>>>> https://vimeo.com/artkill/dropletsrnd
>>>>
>>>>
>>>> then Olivier is right on the money, you need to force the particle
>>>> trajectory with a POPVOP using a double cross product and afterwards use
>>>> VDB volumes so that the droplets merge together properly . It´s not an
>>>> obvious tool to create, though, and it will take some research and
>>>> development on your side, so be sure it´s something you will reuse
>>>> before
>>>> going into it.
>>>> Javier Meroño
>>>>
>>>> From: parker.jon at gmail.com
>>>>> Date: Tue, 19 Jan 2016 12:03:42 -0500
>>>>> To: sidefx-houdini-list at sidefx.com
>>>>> Subject: Re: [Sidefx-houdini-list] water droplets running off the side
>>>>> of a bottle
>>>>>
>>>>> How about scattering some points around your surface, then scatter a
>>>>> separate group near the bottom of your object and use the
>>>>> findShortestPath node to draw lines that connect them. The lines
>>>>> should follow the contours of your object in a fairly realistic way
>>>>> and you can then just animate the droplets to follow the curve paths,
>>>>> no simulation needed.
>>>>>
>>>>> Jon
>>>>>
>>>>> On Tue, Jan 19, 2016 at 10:46 AM, Ron Schab wrote:
>>>>>
>>>>> jep particles or u can have a look at this thing here:
>>>>>>
>>>>>> https://www.orbolt.com/asset/SideFX::vfx_rain
>>>>>>
>>>>>>
>>>>>> SideFx-made HDA that going of the description should offer what u are
>>>>>> after. Haven't downloaded and tested, just remembered seeing it a
>>>>>> while
>>>>>> ago.
>>>>>>
>>>>>> At least should give u some ideas - it's free too
>>>>>>
>>>>>> good luck.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Jan 19, 2016 at 4:25 PM, Olivier Jeannel
>>>>>> facialdeluxe at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>> Double cross product is the way to get some slide on surface based on
>>>>>>
>>>>>>> incoming velocity.
>>>>>>> But there might be a pop doing that, already.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Jan 19, 2016 at 3:52 PM, Srecko Micic
>>>>>>> wrote:
>>>>>>>
>>>>>>> And for moving particles, I did once similar with particle collision
>>>>>>>
>>>>>>>> POP,
>>>>>>>> and Respond set to slide. But not sure will that work in your case.
>>>>>>>> --
>>>>>>>> Srecko Micic
>>>>>>>> 3D Generalist
>>>>>>>> -------------------------------------------
>>>>>>>> Skype: srecko.micic
>>>>>>>> Email: srecko.micic at gmail.com
>>>>>>>>
>>>>>>>> On Jan 19, 2016, at 3:04 PM, Srecko Micic
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> Try to scatter particles on surface. And than use Particle Fluid
>>>>>>>>>
>>>>>>>>> Surface
>>>>>>>> to mesh them, for example?
>>>>>>>>
>>>>>>>> --
>>>>>>>>> Srecko Micic
>>>>>>>>> 3D Generalist
>>>>>>>>> -------------------------------------------
>>>>>>>>> Skype: srecko.micic
>>>>>>>>> Email: srecko.micic at gmail.com
>>>>>>>>> http://sreckom.webworkman.com
>>>>>>>>>
>>>>>>>>> On Jan 19, 2016, at 2:21 PM, Gerbrand Nel <>
>>>>>>>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>> Hey guys
>>>>>>>>>
>>>>>>>>>> This one client called me and needs photo real droplets on a
>>>>>>>>>> bottle
>>>>>>>>>> by
>>>>>>>>>>
>>>>>>>>>> the end of tomorrow.
>>>>>>>>> I've done this in softimage in the past, but I was wondering if
>>>>>>>>>
>>>>>>>>>> anyone
>>>>>>>>>>
>>>>>>>>>> knows of a nice tutorial or demo file of this in houdini?
>>>>>>>>> The static droplets is not the problem,
>>>>>>>>>
>>>>>>>>>> I'm looking for some ideas on how to create the run-offs, how they
>>>>>>>>>>
>>>>>>>>>> pick
>>>>>>>>>
>>>>>>>> other droplets up on the way, and leave a trail behind.
>>>>>>>>
>>>>>>>> Thanks guys
>>>>>>>>>
>>>>>>>>>> G
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